Imporve image lazy loading

file.php

@@ -10,6 +10,15 @@ if (!defined('DOKU_INC')) define('DOKU_INC', __DIR__ . '/../../../');
 if (!defined('DOKU_DISABLE_GZIP_OUTPUT')) define('DOKU_DISABLE_GZIP_OUTPUT', 1); // we gzip ourself here
 require_once(DOKU_INC . 'inc/init.php');
 
+// Close the session early to prevent blocking concurrent requests.
+// PHP sessions are locked by default - if we hold the lock during thumbnail
+// generation, all other requests from this user (including page navigation)
+// will be blocked until we finish. Since we only need session data for ACL
+// checks (which happen before this point via init.php), we can safely close it.
+if (function_exists('session_status') && session_status() === PHP_SESSION_ACTIVE) {
+    session_write_close();
+}
+
 global $INPUT;
 
 $syntax = plugin_load('syntax', 'luxtools');